1. Field of the Invention
This invention relates to an image recording apparatus which records image or character data on a recording medium, such as paper or the like, and especially relates to a recording apparatus which receives image data in the form of an electric image signal from an external apparatus, e.g., a host computer, an image reader, a controller or the like, and outputs high quality visible images.
2. Background
In one type of conventional image recording apparatus (for convenience, generically called a xe2x80x9cprinterxe2x80x9d in this specification), e.g., a laser beam printer which applies electrostatic photography, or the like, generally a host computer (as an example of what is herein termed xe2x80x9cexternal apparatusxe2x80x9d) executes image processing, e.g., a screen process or a dither process and binarizes image data prior to supplying the data to the printer, to obtain halftone images. In another conventional laser beam printer, disclosed in U.S. Pat. No. 4,800,442, a turning-on period of a laser, is controlled by controlling the width of a pulse, in the main scanning direction, representing the image. To express halftone images, the turning-on period of the laser is shortened compared to the turning-on period which would correspond to one image dot (i.e., pure black).
Thus, it is convenient for the host computer to carry out the various kinds of image processes, from the viewpoint of data storing ability and the like. Further, the host computer can send a binary signal to a printer, to lessen the amount of data to be sent, and it is effective for such sending of data.
However, the above-mentioned conventional printers generally have different halftone characteristics from each other depending on types and devices of printers, so that those printers output images having different densities in a given portion even if the same image data is supplied to these printers. For example, the external apparatus supplies a 4xc3x974 dither pattern (an example is shown in FIG. 2) to printers, one of which has an input/output characteristic A (shown as a solid line in FIG. 3), and another of which has another input/output characteristic B (shown as a broken line in FIG. 3). As a result, even if the same image signal, processed with the same dither pattern, is supplied, it can occur that one printer may be unable to express a bright area because a small point is not recorded, while another printer cannot express a dark area because a small white point is covered by other, black marks.
Strictly speaking, not only a halftone image like a photograph but a character image also has the same problem as discussed above. Especially a character image which has small characters expressed with thin lines has this problem because the thin lines are output with lines of different widths by different printers.
Thus, when an image processing system is structured with one host computer and several kinds of printers, there are problems such as an output image on a recording medium, e.g., a paper, being totally blurred and having thin-lined characters, or another output image being totally dark and has crushed characters.
A purpose of the present invention is to provide an image recording apparatus which overcomes the above mentioned shortcomings.
Another purpose of the present invention is to provide an image recording apparatus which can always obtain high quality visible images in accordance with the characteristics of the used to produce the images, even when the system incorporating the apparatus is structured with a common external apparatus and a plurality of kinds of printers having different recording characteristics from each other.
In order to achieve these purposes, an image recording apparatus of the present invention, which receives image data input as an electrical signal from an external apparatus and outputs visible images, includes means for outputting a characteristic signal regarding an image recording characteristic of the recording apparatus, to the external apparatus.
According to another aspect of the present invention is provided an external or output apparatus for an image recording apparatus, wherein the external apparatus deals with a recording characteristic signal from the recording apparatus as a gradation correction signal for halftone images.
According to another aspect of the present invention is provided an image processing system which includes an image recording apparatus having means for outputting a characteristic signal regarding an image recording characteristic of the recording apparatus, and an external apparatus which deals with the characteristic signal output from the recording apparatus as a gradation correction signal for image data.
Thus, in an apparatus constructed in accordance with these aspects of the invention, information about recording characteristics which are different for respective printers is output to an external apparatus, e.g., a host computer, a controller, or the like, as a recording characteristic signal, and the external apparatus makes a suitable correction, corresponding to the respective recording characteristics to image data for each of the printers in response to the respective recording characteristic signals, and supplies suitably corrected image signals to the recording apparatus.
As a result, the external apparatus is able to maintain output images in constant high quality regardless of the differences among the various kinds of printers.
The foregoing summary of certain advanced features of the invention is provided in order that the detailed description of the embodiments thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional features of the invention that will be described in that detailed description with reference to the accompanying drawings. Those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for designing other structures or methods for carrying out the purposes of the invention. It will be understood what the claims are to be regarded as including such other constructions and methods as do not depart from the spirit and scope of the invention.